1. Field of the Invention
This invention relates to a process for conversion of feedstock comprising lower aliphatic alcohols, carbonyls, ethers or analogues thereof to product comprising hydrocarbons. The process comprises contacting, under conversion conditions, said feedstock with a catalyst comprising a synthetic, thermally stable, molecular shape selective, active form of crystalline material designated ZSM-58.
2. Description of Prior Art
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversions. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described as a rigid three-dimensional framework of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li is equal to unity. One type of cation may be exchanged either entirely or partially by another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic aluminosilicates. These aluminosilicates have come to be designated by convenient symbols, as illustrated by zeolite ZSM-5 (U.S. Pat. No. 3,702,886).
The use of certain zeolites as catalyst components is taught in U.S. Pat. No. 4,305,808, for example.
The silica-to-alumina ratio of a given zeolite is often variable; for example, zeolite X (U.S. Pat. No. 2,882,244) can be synthesized with a silica-to-alumina ratio of from 2 to 3; zeolite Y (U.S. Pat. No. 3,130,007) from 3 to about 6. In some zeolites, the upper limit of silica-to-alumina ratio is virtually unbounded. Zeolite ZSM-5 is one such material wherein the silica-to-alumina ratio is at least 5. U.S. Pat. No. 3,941,871 discloses a crystalline metal organo silicate essentially free of aluminum and exhibiting an x-ray diffraction pattern characteristic of ZSM-5 type aluminosilicate. U.S. Pat. Nos. 4,061,724; 4,073,865 and 4,104,294 describe microporous crystalline silicas or organo silicates wherein the aluminum content present is at lower levels.
A number of U.S. patents teach heteroatom feed conversion. Examples of these are U.S. Pat. Nos. 3,894,104, 3,894,106, 3,894,107, 3,899,544, 3,965,205, 4,046,825, 4,156,698 and 4,311,865. Methanol is converted to gasoline in U.S. Pat. Nos. 4,302,619, 3,928,483 and 4,058,576 as examples. Methanol is converted to olefins and/or aromatics in, for example, U.S. Pat. Nos. 3,911,041, 4,025,571, 4,025,572, 4,025,575 and 4,049,735.